FIG. 1 is a diagrammatic view of a known type of measuring chain. The measuring chain 1 comprises a detector 10 connected to a pulse processing unit 12 and/or a fluctuation processing unit 14 by means of an impedance-adapted cable 16 and an amplifier 20 able to transform the current pulses of the signal furnished by the detector 10 into voltage pulses. The detector 10 may be a proportional counter able to measure neutron fluxes. When the neutron flux is low, the signal of the detector shall preferably be processed by a pulse processing unit. On the other hand, when the flux is higher, the signal may be processed by a fluctuation processing unit, this unit being sensitive to the quadratic variations of the signal.
Control of the proper functioning of the measuring chains and the validation of the signals delivered are currently carried out by using various techniques.
As regards the instrumental portion of the measuring chain, this involves control of the serviceable voltages of the devices comprising the chain, such as the amplifier, control of the correct connecting of the cables which connect these devices together, or even the verification of the minimum and maximum counting thresholds of the chain.
As regards the electronic devices for processing detection signals, test pulse generators are used.
In certain cases, horizontal projections are made of curves characteristic of the detectors of counting chains. By way of example, for the source level measuring chains of nuclear power stations, that is for measuring chains carrying nuclear radiation low flux counting, discrimination curves are plotted. On the basis of these curves, the slope of a detection degree or the detector(s) is read. If this slope expressed as a percentage is outside an authorised variation field, the detector needs to be changed.
This method has a relatively empirical character and does not make it possible to diagnose the verified defect or malfunctioning or anticipate its appearance.
Irrespective of the method currently used for validating the signal of the measuring chain, generally speaking, it appears that this validation requires the inhibition or transitory stoppage of the measurements.
Furthermore, the controls carried out render it difficult to take account of the ageing of the components or anticipate their replacement.
One object of the present invention is accordingly to offer a system and method for validating the signals of a radiation measuring chain not exhibiting the limitations and drawbacks mentioned above.
Another aim is also to offer a validation system which does not require the stoppage of radiation measurements or the halting of installations equipped with the measuring chain.
Another aim is to offer a system able to detect any possible deterioration of the sensor or detector of the measuring chain, even before the consequences of this deterioration concerning the validity of the signal become too significant.
Finally, another aim is to offer a system able in certain cases to determine the cause or localisation of the detected malfunctioning.